The present invention relates to siloxane emulsions, in particular siloxane-in-water emulsions which are capable of allowing efficient deposition of siloxanes on substrates.
Siloxane emulsions are known in the art and have been used in a large number of applications. It is particularly relevant to the present invention that siloxane emulsions are used in applications where it is intended to deposit the siloxane onto substrates from aqueous compositions. Examples include textile treating processes, hair conditioner compositions and the like. However the efficiency of deposition is not usually very high especially in diluted conditions. There is a need to provide siloxane emulsions which allow an improved deposition rate of siloxanes onto substrates, especially negatively charged substrates. The present invention is particularly concerned with the deposition of polydiorganosiloxanes. Especially of interest are polydiorganosiloxanes which do not have special functional groups such as amine, carboxy or epoxy, particularly polydihydrocarbyl siloxanes are of interest.
In prior art compositions, siloxanes incorporated in an emulsion, maybe in a micro-emulsion form, that is to say the silicone is present as liquid droplets having a droplet size less than the wavelength of visible light and so the emulsion is substantially transparent or in macro-emulsions form where the siloxane droplets tend to be larger. The siloxanes before emulsification are usually those having relatively low viscosities because those with higher viscosities are more difficult to handle during the process of manufacturing the emulsion product.
Higher viscosity siloxanes are usually preferred for deposition, as they have a more dramatic effect when deposited onto substrates. For example they give improved conditioning effect on hair, greater substantivity etc.
In CA 0953058, an emulsion of reactive siloxane and an emulsion of a silicone polymer are used to impart onto fibre products a softening effect. In EP 432951 a shampoo composition comprises an emulsion of a non-volatile silicone in addition to a cationic derivative of guar gum. Although no specific details are given of the efficiency of silicone deposition, it can be calculated that in the applications described only partial deposition of the silicone is achieved, resulting in a waste of raw materials. In EP 798332 there is described an oil-in-water aqueous organopolysiloxane emulsion composition as a uniform dispersion which comprises 100 parts by weight of certain organopolysiloxane, from 0.5 to 30 parts by weight of a cationic surfactant which is a certain quaternary ammonium compound, from 10 to 300 parts by weight of water, wherein the organopolysiloxane is dispersed in the water in the form of particles having an average diameter of from 3 to 100 micrometer. This is developed especially to be suitable as additive in cationic hair-care compositions.
There is a need to find an emulsion system for siloxanes which will enable improved levels of deposition of the siloxane onto substrates.
It has been found surprisingly that the use of certain emulsifiers allows improved deposition of siloxanes.
According to one aspect of the invention there is provided an oil-in-water emulsion composition comprising:
(a) 0.5% to 20% by weight of a cationic emulsifier as the main emulsifier in the emulsion
(b) up to 75% by weight of a siloxane in dispersed phase with average particle size of no more than 2.5 micron and
(c) water
wherein the siloxane is liquid at 25xc2x0 C. and has units according to formula (1),
RaSiO4xe2x88x92a/2xe2x80x83xe2x80x83(1)
wherein R is selected from hydrocarbon and hydroxyl groups and a has a value of from 0 to 3, with an average value of from 1.85 to 2.20, and wherein the cationic emulsifier does not have a halogen containing counter ion.
In the emulsion, the siloxane droplets are preferably incorporated to be in the form of a macro-emulsion. The average siloxane droplets are preferably from 0.2 xcexcm to 2.5 xcexcm, more preferably 0.3 to 2 xcexcm.
The siloxane has units according to formula (1) above, and is preferably a polydihydrocarbyl siloxane consisting essentially of such units (1), most preferably consisting only of said units (1). Mixtures of several siloxane polymers may be used. It is however preferred that siloxanes as described above are the only organosilicon compounds present in the emulsion.
Particularly preferred siloxanes are linear or cyclic siloxanes of the general formulae (2) or (3)
xe2x80x83Rxe2x80x94(SiO(R)2)mxe2x80x94(SiO(R1)bR2xe2x88x92b)nxe2x80x94SiR3xe2x80x83xe2x80x83(2)

wherein R is as defined above, preferably alkyl, aryl or alkenyl, more preferably having 1 to 20 carbon atoms, most preferably 1 to 6 carbon atoms, and particularly methyl, phenyl or vinyl, R1 is a siloxane side chain of the general formula (4)
xe2x80x94Oxe2x80x94(SiO(R)2)mSiR3xe2x80x83xe2x80x83(4)
m is an integer with a value of from 0 to 100,000, preferably 100 to 5,000,
n is an integer with a value of from 0 to 100, preferably 0,
b has a value of 1 or 2, preferably 0.
It is preferred that siloxanes have the general formula (2) and have end groups which are selected from xe2x80x94Si(Rxe2x80x3)2OH or xe2x80x94SiRxe2x80x33 wherein Rxe2x80x3 is as R above, with the exception of hydroxyl.
Preferred siloxanes have a dynamic viscosity of from 1 to 1,000,000 mPaxc2x7s at 25xc2x0 C., more preferably 10,000 to 1,000,000 mPaxc2x7s, even more preferably 30,000 to 750,000 mPaxc2x7s, most preferably 40,000 to 300,000 mPaxc2x7s. Especially preferred siloxanes are polydimethyl siloxanes or polydimethyl polymethyl phenyl siloxanes e.g. cyclic polydimethyl siloxanes such as octamethyl cyclotetrasiloxane and decamethyl cyclopentasiloxane; linear siloxanes such as xcex1,xcfx89 silanol end-blocked polydimethyl siloxane, xcex1,xcfx89 trimethyl silyl end-blocked polydimethyl siloxane, dimethyl siloxane methyl phenyl siloxane copolymers, dimethyl siloxane methyl alkyl (C12-18) siloxane copolymers, branched siloxane polymers and vinyldimethyl silyl end-blocked polydimethyl siloxanes.
Emulsification is effected using a cationic surfactant not having a halogen in the counter ion as the main surfactant, preferably as the only surfactant. Preferred cationic surfactants have counter ions selected from methosulphate, etho-sulphate, acetate, tosylate, phosphate or nitrate. Examples of suitable cationic surfactants include fatty acid methylammonium methosulphate; fatty acid methylammonium ethosulphate; fatty acid methylammonium acetate; derivatives thereof e.g. ethoxylated fatty acid methylammonium methosulphates.
It is preferred to use a secondary emulsifier in conjunction with the cationic emulsifier and further additional emulsifiers may also be used. These secondary or additional emulsifiers may be-nonionic, but preferably are also cationic emulsifiers, most preferably of the type described above. The total amount of emulsifier used in an emulsion according to the invention is from 0.5 to 20% by weight based on the weight of the emulsion, preferably 2 to 12%, more preferably 3 to 10%.
The amount of siloxane incorporated in an emulsion according to the invention is up to 75%, but preferably is from 30 to 65%, more preferably 50 to 60% by weight based on the total weight of the emulsion. Preferably the weight ratio of siloxane over the total amount of emulsifiers used is from 3:1 to 120:1, preferably 3:1 to 30:1.
It is to be understood however that in applications the emulsions are preferably diluted for use in an environment which may contain a multitude of other ingredients. The dilution level will depend on the amount of deposition which is desired and the process of deposition. Suitable dilutions may be such that the siloxane in the application medium is present in concentrations from 0.001% to 50%, preferably for most applications 0.1 to 5%. An intermediate dilution step may be obtained by formulating an emulsion according to the invention into a product for sale to the end-user, e.g. a shampoo or polish formulation which is further diluted by the end-user in the actual application to the substrate, e.g. in a shower.
The emulsions may also contain one or more optional ingredients, selected from electrolytes, non-aqueous solvents, pH buffering agents, perfumes, perfume carriers, fluorescers, dyes, colorants, hydrotropes, antifoaming agents, antiredeposition agents, polymeric and other thickeners, viscosity modifiers, enzymes, optical brightening agents, opacifiers, anti-shrinking agents, anti-wrinkle agents, anti-spotting agents, germicides, fungicides, anti-oxidants, anti-corrosion agents, antistatic agents, sunscreens, colour care agents and anti-yellowing agents.
It was found that surprisingly the emulsion of the present invention allowed deposition of siloxanes onto substrates, especially negatively charged substrates, in much improved levels. It has been shown that deposition rates of siloxanes onto substrates can be close to 100% or even up to 100% in some cases. Suitable substrates include fibres, keratinous and others, e.g. wool, cotton, hair, synthetic fabrics, metal substrates, e.g. car bodies, wooden and synthetic hard surfaces, e.g. furniture etc. Substrates which are particularly suitable are negatively charged substrates.
In another aspect, the invention provides a process for depositing a liquid siloxane having units according to the formula
RaSiO4xe2x88x92a/2
wherein R is selected from hydrocarbon and hydroxyl groups and a has a value of from 0 to 3, with an average of from 1.85 to 2.20 which comprises contacting a substrate with an oil-in-water emulsion according to the invention. In particular the process uses a diluted form of the emulsion, e.g. having from 0.001 to 50% siloxane. This dilution may be in an aqueous or non-aqueous medium.
It was also found that the emulsions were particularly useful for applications where corrosion of the apparatus used for the deposition was an issue, as no corrosive problems exist which are due to the use of these emulsions.